1. Field of the Invention
The present invention relates to a novel styrylcoumarin derivative, and more specifically, it relates to a photosensitizer comprising a styrylaminocoumarin derivative which functions as a photosensitizer (a sensitizing dye) for a polymerization initiator and/or a crosslinking agent, a photopolymerizable and/or photocrosslinkable photosensitive composition using the photosensitizer, and a hologram recording medium containing the photosensitive composition as a main component.
2. Related Background Art
With the development of triplet sensitizers and dye lasers, various novel coumarin compounds have been synthesized. Above all, ketocoumarins have absorption maximum ranging from 330 nm to 470 nm and so they have been developed as effective triplet sensitizers Tetrahedron, 38, p. 1211 (1982)!.
In consequence, nowadays, the coumarin compounds have been widely used as the photosensitizers for polymerization initiators such as diphenyliodonium salts, triazine, peroxides and halogen compounds. Above all, compounds represented by the formulae (1) to (3) are known as preferable photosensitizers in a photosensitive system using an argon laser at 488 nm. ##STR1##
However, these dyes have absorption maximums in a wavelength region shorter than 488 nm, and a wavelength of 514.5 nm for the argon laser is their absorption edges. Therefore, it is necessary to enhance their sensitivity. In order to enhance the sensitivity of a photosensitive material, an absorbance of the photosensitive material is required to be increased, and as a conventional technique for increasing the absorbance, there has been only one method of increasing the amount of a dye.
In recent years, for the purpose of solving these problems, it has been suggested to use a styrylcoumarin compound represented by the following structural formula (4) as a photosensitizer (a sensitizing dye) Polymer Engineering And Science, 23, p. 1022 (1983)!. However, the suggested photosensitizer is not sufficiently suitable for exposure at 514.5 nm by the argon laser. ##STR2##